This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for METHOD AND CIRCUIT FOR CONTROLLING POWER OF AUDIO PROCESSOR IN MONITOR earlier filed in the Korean Industrial Property Office on the 19th of Mar. 1997 and there duly assigned Serial No. 9404/1997.
1. Field of the Invention
The present invention relates in general to a monitor which is used as a video display apparatus of a computer system and has an audio signal output function, and more particularly to a technique for controlling power of an audio processor in the monitor, in which the supply of power to the audio processor is controlled according to an operating mode of a display power management system (referred to hereinafter as DPMS).
2. Description of the Related Art
Generally, a monitor utilizes vertical and horizontal synchronous signals to display an output signal from a computer system on its screen.
To this end, the computer system outputs the vertical and horizontal synchronous signals to the monitor, together with data to be displayed on the screen of the monitor.
On the other hand, a relatively large amount of time is required from the turning on of the computer system until the normal operation thereof.
It is likely that the computer system may not be continuously used by the user while it is turned on. For example, with the computer system turned on, the user may take a rest while working or not work for a certain amount of time due to other affairs. In these cases, a large amount of power is unnecessarily consumed.
In order to solve the above-mentioned problem, the computer system checks on the basis of the input of a key signal whether it is being used by the user, and operates in a proper manner in accordance with the checked result. Namely, when the computer system is not being used by the user, it operates sequentially in a normal mode, a standby mode, a suspend mode and a power off mode with the passage of time in which the computer is not being used so as to reduce power consumption. When the computer system is again used by the user, it begins operating again directly in the normal mode.
A DPMS has been proposed by the Video Electronics Standard Association (VESA) in the U.S.A. to manage power of a monitor according to the current mode of the computer system to reduce power consumption.
The DPMS is adapted to manage power to various components of the monitor according to a use state of the computer system. The computer system selectively outputs horizontal and vertical synchronous signals according to an operating mode of the DPMS, and the monitor selectively operates in the normal mode, standby mode, suspend mode and power off mode according to the presence of horizontal and vertical synchronous signals from the computer system.
In other words, the monitor operates in the normal mode when the computer system outputs both the horizontal and vertical synchronous signals. The monitor operates in the standby mode when the computer system outputs only the vertical synchronous signal. Also, the monitor operates in the suspend mode when the computer system outputs only the horizontal synchronous signal. Further, the monitor operates in the power off mode when the computer system does not output either the horizontal synchronous signal or the vertical synchronous signal.
It is commonly prescribed that power consumption of the DPMS be about 80-100 W in the normal mode of the monitor, 65 W or less in the standby mode of the monitor, 25 W or less in the suspend mode of the monitor and 5W or less in the power off mode of the monitor.
On the other hand, with the introduction of multi-media techniques, the computer system comprises an audio card for outputting a desired audio signal, and the monitor inputs the audio signal from the audio card, amplifies the inputted audio signal and outputs the amplified audio signal to a speaker.
To this end, the monitor comprises an audio processor including a pre-amplifier for amplifying an audio signal from the audio card in the computer system, and a power amplifier for amplifying an output signal from the pre-amplifier and outputting the amplified signal to the speaker.
In an earlier circuit for controlling the power of an audio processor in the monitor, the audio processor comprises a preamplifier for amplifying left and right audio signals of left and right channels from the audio card in the computer system in response to a level adjustment signal from an audio level adjustment unit and a power amplifier for amplifying output signals from the preamplifier and outputting the amplified signals to a pair of speakers.
A power supply circuit is adapted to supply operating voltages to the preamplifier and the power amplifier and includes a power supply for supplying alternating current, a diode for rectifying an output AC voltage from the power supply into a direct current and a capacitor for smoothing an output DC voltage from the diode and supplying the smoothed DC voltage as the operating voltages to the preamplifier and the power amplifier.
Normally, the power supply in the power supply circuit is a switching mode power supply which supplies AC power according to the current operating mode. The output AC voltage from the power supply is rectified into a DC voltage by the diode and smoothed by the capacitor and supplied as the operating voltages to the preamplifier and power amplifier.
Under this condition, the left and right channel audio signals from the computer system are applied to the preamplifier and the preamplifier amplifies the signals by an amplification factor which is determined by the audio level adjustment unit.
The left and right audio signals amplified by the preamplifier and further amplified by the amplifier are outputted to the pair of speakers. As a result, the user can listen to the left and right channel audio signals from the computer system through the monitor.
The output power from the power supply circuit is varied according to the operating mode of the monitor used with the audio processor.
When the monitor operates in the normal stand-by mode, the power supply in the power supply circuit normally operates to supply rated voltages to the preamplifier and power amplifier.
However, in the case where the monitor operates in the suspend or power off mode, the output voltage from the power supply is lower than the normal value, resulting in the supply of voltages lower than the rated voltages to the preamplifier and power amplifier.
For this reason, the preamplifier and power amplifier are operated normally in the normal and stand-by modes, but, in the suspend and power off modes, because of the supply of voltages lower than the rated voltages, they may be erroneously operated and a phenomenon such as an abnormal oscillation may occur. These occurrences may be unpleasant to the user.
Furthermore, because voltages lower than the rated voltages are continuously applied to the preamplifier and power amplifier, a large amount of power is unnecessarily consumed even in the suspend and power off modes and as a result, the prescribed power consumption of the DPMS in the suspend and power off modes can not be satisfied.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a technique for controlling the power of an audio processor in a monitor, in which rated operating power is supplied to the audio processor in normal and standby modes and blocked in suspend and power off modes.
In accordance with one aspect of the present invention, there is provided a method for controlling power of an audio processor in a monitor, comprising the first step of determining an operating mode of the monitor according to the presence of horizontal and vertical synchronous signals from a computer system; and the second step of controlling the supply of operating power to the audio processor according to the operating mode of the monitor determined in the first step.
In accordance with another aspect of the present invention, there is provided a circuit for controlling the power of an audio processor in a monitor, the audio processor processing an audio signal from a computer system and outputting the processed audio signal to a speaker, the circuit comprising: a power supply circuit for supplying operating power to the audio processor; a microcomputer for controlling an operating mode of the monitor according to an operating mode of the computer system and adjusting an output volume of the audio processor; and power switching unit, operated under the control of the microcomputer, to supply the operating power from the power supply circuit to the audio processor upon the operating mode of the monitor being in a normal mode or a standby mode and to block the operating power from the power supply circuit to the audio it processor upon the operating mode of the monitor being in a suspend mode or a power off mode.